In general, the soldering of printed circuit board built in a consumer electrical appliance like a display device such as a television receiver or the like and a picture recording reproduction apparatus such as a video recorder has been often performed by a flow soldering to mass-produce the corresponding printed circuit boards at a reasonable price.
The flow soldering is a soldering method having a mass production property superior to other soldering because it can solder the whole surface of the printed circuit board at once. In an automatic soldering apparatus that performs the soldering using the flow soldering, various kinds of processing apparatuses such as a preheater, a solder bath, cooling device and the like have been provided. These processing apparatuses are provided with a conveying chain that conveys the printed circuit board and a conveying portion that has a frame guiding the conveying chain to the corresponding processing apparatuses. Such an automatic soldering apparatus performs preheating while the printed circuit board to which flux has been applied by a fluxer or the like is conveyed using the conveying chain, adheres solder thereon in a solder bath, and cools the printed circuit board by the cooling device so that the solder can be formed on a desired position of the printed circuit board.
Unless the solder is formed on a predetermined position of the printed circuit board with accuracy, solder bridge in which the solder is adhered to a position except for the predetermined position or insufficient solder in which no solder is adhered to the predetermined position occurs. Therefore, a conveying portion which fixes the printed circuit board securely on the predetermined position and conveys it is necessary for the automatic soldering apparatus.
Such automatic soldering apparatus, however, has a problem such that the conveying portion is heated because a preheating step by the preheater and a solder-adhering step by the solder bath are carried out and an expansion and contraction occurs based on difference of any thermal expansion between the chain and a frame which constitutes this conveying portion so that a position of the printed circuit board conveyed by the conveying portion is deviated from the predetermined position.
A patent document 1 discloses a conveying device for soldering which is provided with a cooling duct inside a frame. According to this conveying device for soldering, the cooling duct is provided in the frame and a cooling fluid such as air and water is supplied to this cooling duct and is passed therethrough. This can force the frame heated by the preheater and the solder bath to be cooled.
A patent document 2 discloses a conveying device for an automatic soldering, which is provided with a deviation absorption means for absorbing the deviation based on the expansion and contraction of the conveying portion. According to this conveying device for automatic soldering, a pair of frames provided outside of the solder processing apparatus, a supporting bar being put across the pair of frames, and the deviation absorption means that is provided between the supporting bar and the pair of frames and absorbs the deviation based on the expansion and contraction of the frame are provided. This can prevent any thermal distortion of the frame that is heated by the preheater and the solder bath.